Ti-IF steel sheet having excellent surface appearance

摘要

PROBLEM TO BE SOLVED: To provide a low-cost Ti-IF steel sheet excellent in external surface appearance without deteriorating high press formability. ;SOLUTION: When N quantity in the surface nitrided layer at an arbitrary point on a cold rolled sheet of Ti-added steel is represented by C1 wt.% and N quantity in the surface nitrided layer at a position at a distance of at least ≥1 mm from the above arbitrary point along a sheet-width direction is represented by C2 wt.%, the absolute value Cd of the difference between C1 wt.% and C2 wt.% is regulated so that Cd=|C2%-C1%|≤0.002 wt.% is satisfied, where the surface nitrided layer is defined by the following equation: (thickness of surface nitrided layer of cold rolled stock) (μm/one side)=3500×(sheet thickness of cold rolled stock)/(slab thickness).;COPYRIGHT: (C)1999,JPO